This relates generally to communications links, and more particularly, to high-speed input-output (I/O) communications links.
A typical communications link includes a transmitter (TX) module, a receiver (RX) module, and a channel that connects the TX module to the RX module. The TX module transmits a serial data bit stream across the channel to the RX module. Typical high-speed transmit data rates can be as high as 10 Gbps (gigabits per second). Communications links operating at such high data rates are often referred to as high-speed serial links or high-speed I/O links.
Circuit simulation tools such as SPICE have been used to simulate the behavior of communications links. The TX module of a communications link generally includes a driver circuit. SPICE can simulate the deterministic behavior of the driver circuit, but neglects non-deterministic effects such as noise and jitter. Simulating a communications link at a transistor level using HSPICE can often take hours or days for sufficient test coverage. Such long testing times are undesirable.
Behavior-based simulation tools have been developed to overcome the shortcomings of HSPICE. The pre-emphasis equalization link estimator (PELE) available from Altera Corporation of San Jose, Calif. is an example of a behavior-based simulation tool. The PELE takes into account deterministic characteristics and performs simulations based on one-dimensional statistical modeling (e.g., this tool models deterministic sources that affect the timing but not the amplitude of transmitted signals) to determine the optimal coefficients for TX pre-emphasis and RX linear equalizations. As a result, the PELE and other conventional behavior-based simulation tools are not always able to model high-speed communications links such as links that operate at data rates greater than 10 Gbps as accurately as desired, because random characteristics such as random jitter and noise are not taken into account.
It would therefore be desirable to be able to provide an improved simulation tool that can effectively simulate modern high-speed communications links.